ResearchGate has the "emailing other researchers" feature built in so deeply, in fact, that it will email other researchers in your name automatically. Without you asking it to. Without your permission. Even after you die.

A site that makes LinkedIn's dark patterns look responsible is not the answer.

As a professional without access to academic libraries, this is my go-to method for obtaining papers, so I'm glad you brought it up. But it's not without limitations. Last year I was researching some crypto proving methodologies, and discovered the author was dead. I guess he's probably not going to get back to me...

'Many authors will be happy to email you a copy of their paper'. Posting the requested copy was the rule in the '60s and earlier. This could lead to impressive stamp collections. I wonder if Dr. Lowry took up philately. Most cited paper of all time - Protein Measurement with the Folin Phenol Reagent (Lowry, O. H., Rosebrough, N. J., Farr, A. L., and Randall, R. J. (1951) J. Biol. Chem.193, 265–275)

My former advisor keeps his .edu webpage full of pre-print versions of every paper that he has published. I'm not sure if every journal is okay with this, but I'm also not positive that he would stop if prompted. He'd probably just target other journals.

True, but I doubt that would scale, for popular papers that got press coverage. Authors could automate, of course. But do for-profit journals limit reprint distribution?

In my field (computer graphics) most conferences have put clauses allowing authors to host the submitted version of the paper in their websites. Far from ideal, but some compromises from the part of the publishers have been made.

1. Many of the authors I'm interested in are dead. The paywall dates to 1924.

2. I've had authors claim they don't have right (or copies) of works. Mind, one of those is a well-known idiot, but still.

Friction reduction of Sci-Hub is amazing.

http://copyright.cornell.edu/resources/publicdomain.cfm

I simply do a web search for the exact quoted title, and usually find a PDF floating somewhere. Often on the author's website.